Actuator



8, 1944. w. A. v. THOMSEN 2,355,185

ACTUATOR Filed March 19, 1941 2 Sheets-Sheet 1 I I V IINVENTOR I v 5 A 52 M'l/z'arzAVYZmsezz Aug. 8, 19 44. v w v THQMSEN 2,355,185

ACTUATOR Filed March 19, 1941 2 Sheets-Sheet 2 II II imam.

. INVENTOR WY/lt'am 141(720222562? Patented Aug. 8, 1944 ACTUATORWilliam A. Thomsen, Monte lair, N. J assignor to Specialties DevelopmentCorporation, Bloomfield, N. J., a corportion of New Jersey ApplicationMarch 19, 1941, Serial No. 384,047

13 Claims.

The present invention relates to automatic-fire extinguishing systems,and more particularly to a device for use with such systems, designed toactuate the systems in response to a variety of predetermined conditionsattending the beginningof, or which may be the cause of a fire.

Fire extinguishing systems designed to protect a given localitygenerally comprise means to store a fire extinguishing medium, means todistribute the medium, and means to release the medium when required.The releasing means may be operable either manually or automatically, orboth.

Automatic releasing means heretofore used have been somewhat limited intheir usefulness, insofar as they usually have been responsive to onlyone of a number of possible conditions accompanying a fire, such as apredetermined fixed temperature, or a rise in temperature.

As fires may be started by any one of a number of causes, and undervarying circumstances, the desirability will be apparent of providingfor the responsiveness to as many conditions which may be present in theearly stages of a fire as possible, when using an automatic fireextinguishing system.

Such automatic releasing means, asused heretofore, were usuallyresponsive only 'to a single predetermined condition. This conditionusually was pretty close to that of an actual fire in order to insurethe functioning of the fire extinguishing system in any case. It is, ofcourse, very desirable fcr any extinguishing apparatus to subdue a firein its earliest stages, and possibly before it has had the opportunityto start.

,In order to accomplish this, I realized that an automatic device forthe actuation of a fire extinguishing system should be responsive to avariety of conditions, preferably associated with phenomena occurring inthe incipient stages of the conditions which precede a fire. 1

Another object of the invention is to provid an activator for anautomatic fire extinguishing system which is highly sensitive andreliable for a plurality of given conditions associated with fire.

It is still another object of theinvention to provide anactivatorofthetype referred to, which,

portion vertical thereto.

of the supporting members are arranged in a' spaced parallelrelationship with respect to one in response to each of a number ofpredetermined conditions associated with fire, is adapted to produce anactivating pressure impulse.

It is still another object of the invention to 5 provide an'activator,as above, which is, at all times, operative with respect to at least oneof a number of given activating conditions, regardless of any previousresponses which may have been caused by any of the other conditions.

A further object of the invention consists in the construction andarrangement of the parts of the devicewhereby the foregoing objects maybe accomplished.

Other and further objects, not specifically enumerated above, will beapparent when described present invention.

Figure 2 is a' view in section, taken along the line 2-2 on Figure 4.

Figure 3 is a bottom planview of the device with the cover removed toshow its inside construction.

Figure 4 is a top plan view of the device.

Referring more particularly now to the drawings, there is shown inFigure 1 anactuator I, constructedin accordance with the invention, and

mounted on a surface 2,'such as a ceiling of a room or compartment whichis to be protected by a fire extinguishing system adapted to be actuatedby an actuator of the type to be de-- scribed. At 3 is seen a mountingflange, by means 5 of which the actuator may be secured to'the ceiling2. 'A small bore tubing 4 serves to transmit activating pressureimpulses from the actuator or the device'to pneumatically responsivefire extinguishing medium releasing means, which forms 40 no part of thepresent invention and which is not shown In Figures 2 and 3, theactuator I is shown to have'a cup-shaped body member 5, designed to actas a housingfor the mechanism of the device; A clamping ring 6 may besecured by means of screws 1 into the bottom of thecup-shaped body 5.The ring -6 mounts suitable supporting members 8 and 9, each comprisinga portion parallel to the bottom of the actuator and another Thevertical portions another, and serve as bearing plates for the pivotedelements of the actuator mechanism as will 5 appear presently.

The actuator mechanism comprises an actuating cam l5, pivotable about apin ll carried by the vertical plates just mentioned. A drive spring i2(Figure 2) tends to rotate the cam ID in a counterclockwise direction,being attached to a spring anchor l3 mounted in the vertical bearingplates, at one end, and by a rivet l4 secured to the cam Ill, at theother end. ,The cam II] is kept from rotating'by latching with an offsetportion E5 on a trigger member l6, which is plates. prongedactuatinglever l3 extending above the edge of the vertical portion ofthe bearing plates. The trigger I6 is held in its energized andlatchingposition as shown, by a trigger spring l9, its ends being anchored atthe end of the lever is adjacent the trigger, and on a spring anchorpin' mounted in the bearing plates, respectively.

A trigger tripping member 2|, pivoted at 22, is urged to rotate in aclockwise direction by means of a trip spring 23 supported by thetripping member 2! and by the anchor pin 20. The tripping member 2| isformed witha lever 24 which extends to the outside of the housing 5through a slot 25 in the wall thereof. The lever 24 is adapted tomaintain the tripping member 2! in the position shown, against the forceof the spring 23 by latching outside the housing 5 with a bimetalthermostatic element 26, outlined in dashes in the view of Figure 3. Alatch between the lever 24 and the element 26 is indicated at 21. Thebi-metal element 26 is secured by means of rivets 28'to a member 29adapted to serve as a guard, and which is provided with apertures 10=(Figure 3) along most of its length to facilitate to the lever24 bymeans of an adjusting screw- 3 I,

which is threaded into a projection 32 formed on the housing 5. Theguard and bi-metal assembly as a whole is easily ivotable about thescrew 30,-

when the latter is loosened-sufiiciently. a At 33 is indicated a leverfor resetting the cam= It A slot 34 isprovided inzthe housing 5 -for theextreme-end of the lever 33-which extendsoutside of the housing topermitof the manual resetting of the cam ID. The lever 33 is pivotableabout the rivet I4, referred to above in connection with the drivespring l2.

Between the frusto-conically shaped bottom" or floor 35 of the housing 5and the cam"l0,"two diaphragms are disposed, indicated at 35 and 31-,which are held in place by the clamping-ring '5' and a'spacer ring 33;the diaphragm 35 is being held between the rings 6 and 38, and thediaphragm 31lis held between the spacer ring'38 and the 'floor 35 of thehousing '5. Each of the diaphragms, whichimay be'made of varnished glassfabric to render them flexible and resistant to high temperatures, isprovided centrally and on each side. thereof with a flat rigid spacerdisc 39, the two discs of each diaphragm being held together bya1rivet4ll. It is tobe noticed that no operative-connectionexistsbetween the dia--' phragms, and that the diaphragm 3lyis capableof moving independently of the diaphragm 36-. The diaphragms aremaintained in the position shown in Figure 2 by the forceiof a spring 4|bearing against the disc shown uppermostjin Fige pivoted on a pin 11mounted in the bearing 3 The trigger I6 is formed with a twoure 2 andbeing supported in a recess 42 formed in a boss 43 on the housing 5. Theboss 43 is threaded at 44 to carry the mounting flange 3. A chamber 45,formed between the floor 35 of the housing 5 and the diaphragm 31,communicates with the tubing 4 through an aperture 45 in the floor 55 ofthe housing 5 and through a suitable connecting formation 47 formed inthe floor of the housing.

Tubing 4, as outlined above, may lead to any desired pneumaticallyoperable extinguishing fluid release mechanism (not shown). A con- 1necting member 45 mounted on tubing 4 (Figure 4) serves to connect thedevice with suitable service piping which isinot shown and which may'lead to a pneumatic release mechanism. A

chamber 49, formed between the diaphragms 3G and 31, through passagesand 54 in the spacer ring 38, and through passages 52 and 53 in acoupling formation 54 on the housing 5, is in fluid'flow communicationthrough one side of the coupling 54 with an annular air bulb 55, by wayof a short piping 56. Y

The other side of the coupling 54 opens into a restricted or slow vent51 (Figure 4), which is designed to permit the venting to the atmosphereat a predetermined rate of the otherwise closed space formed by the bulb55 and the chamber 49. The form of vent, illustrated here, is of theexchangeable type which permits of the regulation of the maximumcontemplated venting rate. The vent itself forms no part of theinvention and may assume any desired form as long as it permits of theregulation of the venting rate. The bulb 155, which may consist of ahollow tubular metallic formation havingthin and heat conducting walls,may be mounted concentrically with respect to the housing 5 onsuitableprojections 58 formed peripherally on the housing, and maybeheld there by screws 59. of the projections 58, a wire guard 50 isheld fast by screws 6| threaded into the projections" 58 and holdingdown guard supporting members 62, the whole serving to protect thethin-walled air bulb 55 from mechanical injury.

.A ring-formed metallic frame 63 slipped over the edge .of the housing5, and bent inwardly as at 64, serves to support loosely on the bentinportion 54 ,a thin disc 65,-preferably of sheet mica, which is sodimensioned with respect to the inside diameter of the housing 5 as tobe freely movable upwardly and downwardly therein, and which" is sopositioned as to bear very lightly against the trigger lever. It. Thedisc 55 is protected against accidental outside contact by means of a.convex-shaped wire mesh screen 66 held ,inplace by a ring-type frame 61secured over the frame63 by screws 58 threaded into the resultingtherefrom,'upon reaching the disc 65' through the screen 66, will causean upward movement of the disc 55 (in'Figure 2) and there-- by willcause a temporary movement in a counterclockwise direction of thetrigger lever l8 and the trigger I5; member causes the setting freeofthe eccentric or" cam member I5, whereupon the drive spring 12 Wi lrotate the cam in a counter-clockwise On the other side This movement ofthe trigger phragms 36 and 3'! are thrust'toward the floor 35 of housing5. The chamber 45 is thus subjected to a decrease in its volume, apressure wave or impulse thereby being setup through the tubing 4,wherethrough the impulse is transmitted to a pneumatically operablerelease device (not shown) to operate it. As the cam rotates to itscompletely released position, thatis, to'a position rotated 180counter-clockwise from that shown in Figure 2, the spring 4| by itsaction on the uppermost of the discs 39 (Figure 2), returns thediaphragms to their original and nonactuated position as in Figure 2.The volume of the chamber 49 betweent he two diaphragms 36 and 31 inthis case remains unafiected throughout, since there is no relativedisplacement of the diaphragms. Due to the small diameter of the tubing4, and due to the design of the springs I2 and 4|, considerable time isrequired for the pressure, set up by the movement of the diaphragms, tobe transmitted therethrough. This condition serves to maintain a fairlyhigh pressure in the chamber 45 and to slow up the rotation of the caml0, preventing the immediate snapping around of the cam into its fullyoperated position. This is an intended manner of operation, since apressure, sustained over a period of time, is required to efiect theactuation of the pneumatic device connected thereto. After the completerelease of the cam HL'the trigger'spring 19 returns the trigger IE toits original position. In order to"reset the device, the cam is rotatedback into its latched position with respect to the trigger l6 bymanipulation of the reset arm 33. It is to be understood that only atrue explosion, that is one, which will result in a pressure wave of therequired suddenness will operate the disc 65, the slots 25 and34allowi'n g pressure impulses'having a suddenness less than that due totrue explosions, to create a condition of counter pressure on the insideof the disc. Solutions, other than these slots, to create a similareffect, will suggest themselves to one skilled in the art.

In the absence of an explosion, actuation of the device may also be hadby exposure to a predetermined temperature, whichwill cause thebi-metallic element '26 to .warp and eventually to slide. past theend ofthe .triplever 24. The

tripping member 2| is now free torotate in a clockwise direction due tothe actionof the trip spring 23. v.The tripping member, 21 thereby ismade to impart a rotative movement to the trigger l6, similar to thatcaused by thedisc 65 in the case of an explosion whereby the cam memberI0 is released andan activatingpressure impulse is generated bythediaphr'agms 36 and 31 as before. By proper selectionofthethermostaticelement 26, the actuator may be made to react to any temperature that,may be desired. The adjusting screw,3l is used for close adjustment in atemperature range of about 100,

F.,ufor any given element. For, resetting, following the operation byafixed temperature, the trip lever 24 is pressed-upwardly:simultaneously with the manipulation of the reset arm 33. Both theselevers serve in this case m indicate an operation due to aiixedtemperature If the actuator is subjected to an excessive rate of rise intemperature, that is, one beyonda contemplated rate, the heated air inthe annularbulb expands to a degree which the calibrated vent 51 is notable to accommodate, whereby a pressure is set up, through the tube 56,in the space 49 between the diaphragms 36 and 31. Thediaphragm 31 isthus forcedupwardly to create a pressure impulse in the tubing 4 andtoward a pressure responsive release mechanism which may be connectedthereto. The movement, in this case, of the diaphragm 31', is quiteindependent of diaphragm 36 which remains stationary. l

The construction of the device insures that its operation due to a rapidrise in temperature does not affect its readiness to operate byexplosion or at a fixed temperature. Conversely, the operation of thedevice by an explosion or a fixed temperature does not affect itsoperation by a rise in temperature. The device is, thus, always'operable by too rapid a rise in temperature. This feature, and the factthat the device need not be reset, after an operation due to a givenrate of rise in temperature, are important aspects of the device, whichhave been so recognized bythe board of underwriters laboratories.

It will be recognized that if either an explosion or an excessive rateof rise in temperature for some reason is not capable offcausin'g theactuator to operate to produce a pressure impulse, the bi-metallic fixedtemperature element will act as a reserve protection, positivelyreleasing the actuator when a given hightemperature has beenreached. ,7

The vent, used in conjunction with the actuator, may be of any desiredform, and, in the illustrated case, is of the exchangeable type, whichpermits the adjustment of the venting capacity of the .air bulb 55by achange to another vent of a suitable size. It is therefore possible, in.thecase of, a supervisory system for detecting fires, employing aplurality of actuator devices in accordance with the invention, to haveeach device provided with the size vent best suitedto therequirements-of the locality which it protects. In other fire detectingsystems, which utilize the rate-0f-temperature-rise principle,

a single vent has been used for several actuators,

thereby making each of the actuators equally sensitive, which. is, ofcourse, never quite adequate for a proper supervision of the variouslocalities. The provision of the diaphragm-3! hastheeifect of separatingthe heat responsive air bulb .55 from any other bulbs that may be intheservice conduit connectedto the tubing 5;wherebyonly the relativelysmall volume of airin the bulb 55and the chamber 49 needs to be expandedby heat to'cause a sufiiciently large pressure impulse to beset upthrough the service conduit to obtain an actuation of the system.Thiscondition makes itpossible to use a larger number of actuators onthe same service line thanwas possible heretofore, with a resultant in}crease in the sensitivity of the supervisory'sys tem asa whole. Thisconstruction, too, will ea vent thefentire system from becoming inoperative, should, one

of the bulbs be accidentally punctured The time Ofresponse of anypneumatic mech anism to a given rate of temperaturetincrease largelydepends upon; the length of, tubing :to

w iehi aQ u -w ma 'b ect d an m 1 specification. Finally, whilemyinvention has been illustrated and described with specific referenceto the accompanying drawings, it will be apparent to those skilled inthe art that the invention resides in certain principles of constructionand arrangement which may be embodied in various other forms withoutdeparting in any manner from the spirit and scope of the invention; andI therefore do not wish to be limited-to the specific disclosure, theappended claims.

I claim: 7

1. In an actuator for use with a pneumatically responsive apparatus, thecombination of a housing, chamber means in said housing hav-. ing adiaphragm, spring means supported in the housing yieldinglyopposingmovement of said diaphragm to decrease the volume of, said chambermeans, outlet means for the chamber means adapted for connection toservice tubing, a second diaphragm in the housing adjacent said firstdiaphragm forming a second chamber therewith, spaced means intermediatesaid diaphragms, an air bulb disposed on said housing, a restrictedcalibrated vent for said bulb, means forming a fluid flow communicationbetween said bulb and said second chambensupporting means in thehousing, a camv to actuate said diaphragms carried by the supportingmeans; driving means for but rather to said cam, cam resetting means,means to indicate the position of the cam extending outside the leveradapted to act thereon to release the cam,

releasable trigger trip means on said support having a lever, and anadjustable fixed temperature thermostatic element secured to the housingadapted in its non-actuated position to late with said trip lever.

2. An actuator for use with pneumatically responsive apparatuscomprising in combination: chamber means having a movable wall adaptedby its movement tocause a change in the. volume of said' chamber means;and a plurality of means operatively. associated with said wall formovingsaid wall in a manner to decrease the volume of said chambermeans, each of said plurality of means ,being adapted to be affected byonly one predetermined type of condition associated with fire, and eachbeing independently anddifierentlyresponsive to its respective type ofcondition; said chamber means being" adapted to be in operativeconnection with the pneumatically responding apparatus, whereby upon theresponse of any of said plurality of'means the increased a chamber meanshaving a movable wall adapted by its movement to cause a change in thevolume of said chamber means; a plurality of means operativelyassociated with said wall for moving said wall in a manner to decreasethe volume of said chamber means, each of said plurality of meansadapted to be affected by only one predetermined type of conditionassociated with fire, and each being independently and differentlyresponsive to its respective type of condition; and yieldable meansoperatively associated with said movable wall for resisting theactuation of said movable wall and adapted to effect the restoration ofsaid wall; said chamber means being adapted to be in operativeconnection with the pneumatically responding apparatus, whereby, uponthe response of any of said plurality of means, the increased pressurein said chamber means resulting from a decrease in the volume thereof isadapted to cause the actuation of the pneumatically responsiveapparatus.

4. An actuator for use with pneumatically responsivev apparatuscomprising in combination: chamber means; means responsive to apredetermined rate of rise in temperature forming a movable wall of saidchamber means and being adapted by itsmovement to cause a change in thevolume of said chamber means; explosion responsive means; meansresponsive to a predetermined temperature, each of said three namedresponsive means being differently responsive to its respective type ofcondition, and means operatively associating said two last namedresponsive means with said movable wall in a manner to move said wall todecrease the volume of said chamber means; said chamber means. beingadapted tobe in operative connectionwith the pneumatically respondingapparatus, whereby upon the response. of any of said three namedresponsive means the increased pressure in said chamber means resultingfrom a decrease in the volume thereof is adapted to cause the actuationof the pneumatically responsive apparatus.

5. An actuator for use with pneumatically .responsive apparatuscomprising in combination: chamber means; means responsive to apredetermined rate of rise in temperature forming a movable. wall ofsaid chamber means and being adapted by its movement'to cause a changein the volume of said chamber means; explosion responsive means; meansresponsive to a predetermined temperature; each of said three namedresponsive means being differently responsive to its respective type ofcondition; and means operatively associating said two last namedresponsive means withsaid movable wall in a manner to move said wall todecrease the volume of said chamber means; and resetting means for saidsecond and third namedresponsive means; said chamber means being adaptedto be in operative connection with the pneumatically respondingapparatus, whereby upon the response of any of said three namedresponsive means the increased pressurein saidIchamber means resultingfrom a decrease in the'vol'ume'thereof isadapted to cause the actuationof' the pneumatically responsive apparatus. t

, 6. An actuator for use with pneumatically responsive apparatuscomprising in combination: chamber means having a movable wall adaptedby its movement to cause a change in the volume of said chamber means; anormally r'estrained actuating mechanism operatively associated'with'and adapted upon its release to mov said wall in'a manner to'decreasethe volume of Said chamber means; an explosion responsive member; .aamember responsive toqa predetere mined temperature, each of saidmembersbeing constructed and arrangedto release said mecha-: nism, andeachbeing independently and dilTerentlyresponsive to itsrespective typeof condition; a fluid pressure generator responsive to-a predeterminedrate of rise in temperature; and means connecting said generator influid flow communication with said movable Wall to effect the movementof said Wall independently of said mechanism by fluid pressure in amanner to decrease the volume of said chamber means; said chamber meansbeing adapted to be in operative connection with the pneumaticallyresponding apparatus.

7. An actuator for use with pneumatically responsive apparatuscomprising in combination: chamber means having a pair of movable walls,one of which is adapted by its movement to cause a change in the volumeof said chamber means; a normally restrained actuating mechanismoperatively associated with and adapted upon its release to move saidwall in a manner to decrease the volume of said chamber means; anexplosion responsive member; a member responsive to a predeterminedtemperature, each of said members being constructed and arranged torelease said mechanism, and each being independently and difierentlyresponsive to its respective type of condition; a fiuid pressuregenerator responsive to a predetermined rate of rise in temperature; andmeans connecting said generator in fluid flow communication between saidpair of movable Walls, whereby pressure created in said generator isadapted to efiect movement of the wall adapted to cause a change in thevolume of said chamber means.

8. In an actuator for pneumatically responsive apparatus, thecombination of an air thermostat responsiv to a given rate of rise intemperature adapted to generate a pressure impulse, said thermostathaving vent means, pressure conserving chamber means having a diaphragmmovable by pressure and a second movable diaphragm normallysubstantially adjacent to the first diaphragm operable to move saidfirst diaphragm; mechanical means operatively associated with andoperable to move said second diaphragm; and pressure impulsetransmitting means in operative association with said chamber andadapted to be connected with a pneumatically responsive apparatus,whereby upon a response of said thermostat or upon operation of saidmechanical means said first diaphragm is adapted to set up I a pressureimpulse in said transmitting means to operate the pneumaticallyresponsive apparatus.

9. In an actuator for pneumatically responsive apparatus, thecombination of an air thermostat responsive to a given rate of rise intemperature adapted to generate a pressure impulse, said thermostathaving vent means; a chamber; pressure conserving chamber means havingwalls movable as a unit without change in its volume, one of said Wallsbeing a diaphragm separately movable by pressure and forming a wall ofsaid chamber; means operatively connecting said chamber means to saidthermostat for movement of said diaphragm by pressure; normallyrestrained mechanical means operatively associated with and operable toactuate said chamber means as a unit; pressure impulse transmittingmeans in operative association with said chamber and adapted to beconnected with a pneumaticallyrresponsive-apparatus; and explosionactuated means foractuating said-mechanical means; whereby upon aresponse of 'saidlthermostat or upon operation otsaid mechanical meanssaid diaphragm is-adapted, to set up apressure impulse in saidchamberand said transmitting means to operate the pneumatically responsiveapparatus. l 10, In an actuator forpnemnatically-responsiveapparatus,the combination of an air thermostat responsive to a givenrate of rise in temperature adapted to generate a pressure impulse, saidthermostat having vent means, a chamber; pressure conserving chambermeans having walls movable as a unit without change in its volume,

' one of said walls being a diaphragm separately movable by pressure andforming a wall of said chamber; means operatively connecting saidchamber means to said thermostat for movement of said diaphragm bypressure; normally restrained mechanical means operatively associatedwith and operable to actuate said chamber means as a unit; pressurimpulse transmitting means in operative association with said chamberand adapted to be connected with a pneumatically responsiv apparatus;explosion responsive means; and fixed temperature responsive means; saidtwo last named responsive means being constructed and arranged to effectrelease of said mechanical means; whereby upon a response of saidthermostat or upon operation of said mechanical means said diaphragm isadapted to set up a pressure impulse in said chamber and saidtransmitting means to operate the pneumatically responsive apparatus.

11. In an actuator for pneumatically responsive apparatus, thecombination of chamber means having a movable member; normallyrestrained mechanical means to actuate said movable member in a mannerto decrease the volume of said chamber; means yieldingly resisting theactuation of said movable member in a direction to decrease the chambervolume; pressure impulse transmitting means in operative associationwith said chamber and adapted to be connected with a pneumaticallyresponsive apparatus; and explosion actuated means adapted to effectrelease of said mechanical means to operate said movable member; wherebyupon the release of said mechanical means and upon the movement of saidmovable member the increased pressure in said chamber means resultingfrom a decrease in the volume thereof is adapted to cause the actuationof said pneumatic apparatus.

12. In an actuator for pneumatically responsive apparatus, thecombination of chamber means having a movable member; normallyrestrained mechanical means at one side of said movable memberstructurally connected to said movable member adapted to actuate saidmovable member in a manner to decrease the volume of said chamber; meansat the other side of said movable member yieldingly resisting theactuation of said movable member in a direction to decrease the chambervolume; pressure impulse transmitting means in operative associationwith said chamber and adapted to be connected with a pneumaticallyresponsive apparatus; and fixed temperature responsive means adapted toefiect release of said mechanical means to operate said movable member;whereby upon the release of said mechanical means and upon the movementof said movable member the increased pressure in said chamber meansresulting from a decrease in the volume thereof is adapted to causetheactuation of said pneumatic apparatus 13. In an actuator of the typedescribed, the combination comprising: a casing having an open end, anormallyrestrainedactuating mechanism, means for effecting actuation ofsaid mechanism including an operating member disposed in said casing, adiaphragm member responsive to pressure impulses due to an explosion,said diaphragm member being at the open end of said casing and adjacentsaid operating member for efiecting movement thereof, and slow fluidpressur impulse transmitting means at the open end of said casing,whereby said diaphragm member is affected only by the pressure impulsesof a true explosion.

WILLIAM A. V. THOMSEN.

